Fuel reforming apparatus and method

ABSTRACT

A fuel reforming apparatus includes a reforming reaction section in which a reforming catalyst is disposed, and a reformed fuel distribution chamber. A fuel air mixture of a hydrocarbon fuel and air is reformed in the reforming reaction section. The reformed fuel is supplied from the reformed fuel distribution chamber to chambers of the engine. The adsorbent member is disposed between the reforming reaction section and the reformed fuel distribution chamber. The adsorbent member captures a non-reformed fuel.

This application claims priority from Japanese Patent Application Nos.2003-314367 filed Sep. 5, 2003 and 2004-126029 filed Apr. 21, 2004,which are incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel reforming apparatus and methodfor reforming a fuel air mixture of a fuel and air.

2. Description of the Related Art

For example, Japanese Patent Application Laid-open No. 4-058064 (1992)discloses an engine with a reforming catalyst. In this engine, thereforming catalyst is disposed upstream of a fuel injection valve withinan intake pipe. Further, a fuel feeding valve, an ultrasonic atomizer(an ultrasonic oscillation member), an igniter and a flame extinguisherare disposed upstream of the reforming catalyst within the intake pipe.When the engine is started, a hydrocarbon fuel is fed from the fuelfeeding valve to the ultrasonic sprayer and is atomized into microdroplets by the ultrasonic atomizer. The hydrocarbon fuel is ignited bythe igniter and burns. Flames generated in the intake pipe areextinguished by the flame extinguisher. Then, a heated fuel air mixtureis introduced into the reforming catalyst in which a fuel component tobe sucked into a combustion chamber is obtained by a predeterminedreforming reaction.

However, even if the fuel air mixture is formed by atomizing thehydrocarbon fuel into micro-droplets as described above, it is difficultto uniformly mix the fuel and air. If a nonuniform fuel air mixture isfed to the reforming catalyst, an amount of non-reformed fuel(non-reformed HC) increases. The non-reformed fuel is fed to thecombustion chamber while not reformed by the reforming catalystincreases. If the amount of the non-reformed fuel fed to the combustionchamber increases in such a manner, it is difficult to reduce an exhaustemission.

SUMMARY OF THE INVENTION

The present invention is directed to overcome one or more of theproblems as set forth above.

One aspect of the present invention relates to a fuel reformingapparatus for reforming a fuel air mixture of a fuel and air. Theapparatus comprises: a reforming catalyst for reforming the fuel airmixture; a reformed fuel supply section for supplying a reformed fuelproduced by the reforming catalyst to a predetermined object; andcapturing means for capturing a non-reformed fuel, the capturing meansbeing disposed between the reforming catalyst and the reformed fuelsupply section.

Another aspect of the present invention relates to a method of reforminga fuel air mixture of a fuel and air with a reforming catalyst. Themethod comprises the step of: capturing a non-reformed fuel with anadsorbent material between the reforming catalyst and a reformed fuelsupply section for supplying a reformed fuel produced by the reformingcatalyst to a predetermined object.

The above and other objects, effects, features and advantages of thepresent invention will become more apparent from the followingdescription of embodiments thereof taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a vehicle with a fuel reformingapparatus according to a first embodiment of the present invention;

FIG. 2 is a schematic illustration of the fuel reforming apparatusaccording to the first embodiment of the present invention;

FIG. 3 is a partially sectional view of the fuel reforming apparatusshown in FIGS. 1 and 2;

FIG. 4 is a partially sectional view illustrating an alteration of thefuel reforming apparatus according to the first embodiment of thepresent invention;

FIG. 5 is a partially sectional view of a fuel reforming apparatusaccording to a second embodiment of the present invention;

FIG. 6 is a flow chart for explaining an operation of the fuel reformingapparatus shown in FIG. 5;

FIG. 7 is a partially sectional view illustrating an alteration of thefuel reforming apparatus according to the second embodiment of thepresent invention;

FIG. 8 is a flow chart for explaining an operation of the fuel reformingapparatus shown in FIG. 7;

FIG. 9 is a partially sectional view of a fuel reforming apparatusaccording to a third embodiment of the present invention;

FIG. 10 is a flow chart for explaining an operation of the fuelreforming apparatus shown in FIG. 9;

FIG. 11 is a partially sectional view illustrating an alteration of thefuel reforming apparatus according to the third embodiment of thepresent invention;

FIG. 12 is a flow chart for explaining an operation of the fuelreforming apparatus shown in FIG. 11;

FIG. 13 is a partially sectional view illustrating another alteration ofthe fuel reforming apparatus according to the third embodiment of thepresent invention;

FIG. 14 is a flow chart for explaining an operation of the fuelreforming apparatus shown in FIG. 13;

FIG. 15 is a partially sectional view of a fuel reforming apparatusaccording to a fourth embodiment of the present invention;

FIG. 16 is a sectional view taken along a line XVI—XVI in FIG. 15;

FIG. 17 is a schematic illustration of the fuel reforming apparatusaccording to the fourth embodiment of the present invention; and

FIG. 18 is a schematic illustration of an alteration of the fuelreforming apparatus according to the fourth embodiment of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the fuel reforming apparatus according to the present invention, anon-reformed fuel (non-reformed HC) is captured by capturing meansbetween a reforming catalyst and a reformed fuel supply section.Accordingly, it is possible to prevent the non-reformed fuel from beingsupplied to an object such as an internal combustion engine (acombustion chamber) and the like, and to reduce an exhaust emission.

Preferably, the fuel reforming apparatus of the present inventionfurther includes cooling means for cooling the reformed fuel between thereforming catalyst and the capturing means.

Preferably, the capturing means is disposed in an outer region of apassage connecting the reforming catalyst and the reformed fuel supplysection.

The fuel reforming apparatus of the present invention may furtherincludes a first passage connecting the reforming catalyst and thereformed fuel supply section, a second passage bypassing part of thefirst passage and connecting the reforming catalyst and the reformedfuel supply section, and opening/closing means for opening and closingthe first passage. In such a configuration, the capturing means isdisposed in the second passage and includes an adsorbent material foradsorbing the non-reformed fuel. When an operation of the fuel reformingapparatus is started, the opening/closing means is closed so that thereformed fuel is led from the reforming catalyst only into the secondpassage.

Since a much amount of the non-reformed fuel generally generatedimmediately after a start-up of the fuel reforming apparatus is capturedby the adsorbent material disposed in the second passage, it is possibleto prevent the non-reformed fuel from being supplied to an object suchas an internal combustion engine. Also, if an operational condition ofthe fuel reforming apparatus is stable, an amount of non-reformed fuelreduces and the non-reformed fuel adsorbed in the adsorbent material isreleased from the adsorbent material as a temperature of the adsorbentmaterial rises. Therefore, in this fuel reforming apparatus, at a stagein which the operation of the fuel reforming apparatus becomes stable,the opening/closing means is gradually made to open so that a flow rateof the reformed fuel through the second passage is reduced. Accordingly,it is possible to gradually release the non-reformed fuel from theadsorbent material while taking a long time.

Preferably, the second passage connects a portion of the first passageupstream of the opening/closing means and a portion of the first passagedownstream of the opening/closing means.

The second passage may surround the first passage.

Preferably, the opening/closing means is closed from a start of a fuelreforming operation in the reforming catalyst until a predeterminedperiod has lapsed or until the adsorbent material has reached apredetermined temperature.

Preferably, the fuel reforming apparatus of the present inventionfurther includes non-reformed fuel recovering means for recovering thenon-reformed fuel captured by the capturing means and supplying thenon-reformed fuel to the reforming catalyst again. Thus, it is possibleto surely prevent the non-reformed fuel from being supplied to an objectsuch as an internal combustion engine, and to recover the non-reformedfuel captured by the capturing means and effectively use thenon-reformed fuel again.

Preferably, the non-reformed fuel recovering means includes negativepressure generating means for generating a negative pressure by using aflow of air supplied to the reforming catalyst, and a passage connectingthe negative pressure generating means and the capturing means.

The fuel reforming apparatus of the present invention may furtherinclude heat exchanging means having a reformed fuel passage for leadingthe reformed fuel from the reforming catalyst to the reformed fuelsupply section and a heating medium passage for circulating a heatingmedium to exchange heat between the heating medium and the reformed fuelflowing the reformed fuel passage, and adsorbent material for adsorbingthe non-reformed fuel disposed as the capturing means in the reformedfuel passage of the heat exchanging means.

In such a configuration, the heating medium (coolant) flowing throughthe heating medium passage of the heat exchanging means can adsorb heatfrom the reformed fuel flowing through the reformed fuel passage, sothat a temperature rise of the adsorbent material due to heat of thereformed fuel can be prevented. According to such a configuration, it ispossible to release the non-reformed fuel from the adsorbent materiallittle by little as the time lapses.

Preferably, the predetermined object is a combustion chamber of aninternal combustion engine and the heating medium is part of airsupplied to said combustion chamber.

The method of the present invention is a method of reforming a fuel airmixture of a fuel and air with a reforming catalyst, the methodincluding the step of: capturing a non-reformed fuel with an adsorbentmaterial between the reforming catalyst and a reformed fuel supplysection for supplying a reformed fuel produced by the reforming catalystto a predetermined object.

Preferably, the method of the present invention includes the step ofcooling the reformed fuel between the reforming catalyst and thecapturing means. Preferably, the method further includes the step ofrecovering the non-reformed fuel captured by the adsorbent material andsupplying the non-reformed fuel to the reforming catalyst again.

Preferred embodiments according to the present invention will now bedescribed with reference to drawings.

(First Embodiment)

FIG. 1 is a schematic illustration of a vehicle with a fuel reformingapparatus according to the present invention. The vehicle 100 shown inFIG. 1 has an engine (internal combustion engine) 1 as a power unit. Theengine 1 generates power by combustion of a fuel air mixture containinga fuel component in combustion chambers 3 formed in a cylinder block 2to reciprocate a piston 4 in the respective combustion chambers. In thisembodiment, the engine 1 is configured as a four-cylinder engine as seenfrom FIG. 2 (in FIG. 1, however, only one cylinder is shown).

An intake port of each combustion chamber 3 is connected to an intakepipe 5 a constituting an intake manifold 5, while an exhaust port ofeach combustion chamber 3 is connected to an exhaust pipe 6 aconstituting an exhaust manifold 6. Also, in a cylinder head of theengine 1, an intake valve Vi for opening and closing the intake port andan exhaust valve Ve for opening and closing the exhaust port aredisposed with respect to each of the respective combustion chambers 3.The intake valves Vi and the exhaust valves Ve are operated by avalve-operating mechanism (not shown) preferably having a variablevalve-timing function. Further, in the cylinder head of the engine 1, anignition plug 7 is disposed with respect to each of the combustionchambers 3. Also, the exhaust manifold 6 is connected to a catalyst unit(a three-way catalyst) not shown.

As seen from FIGS. 1 and 2, the intake manifold 5 (respective intakepipes 5 a) is connected to a surge tank 8, and the intake manifold 5 andthe surge tank 8 constitute an air intake system of the engine 1. Also,an air supply pipe L1 is connected to the surge tank 8. The air supplypipe L1 is connected to an air inlet not shown via an air cleaner 9. Athrottle valve (an electronic throttle valve in this embodiment) 10 isincorporated in the air supply pipe L1 between the surge tank 8 and theair cleaner 9.

Further, the air supply pipe L1 is provided with an air flow meter AFMwhich is located between the air cleaner 9 and the throttle valve 10. Areforming air supply pipe (air supply line) L2 is branched from the airsupply pipe L1 at a branched point BP positioned between the throttlevalve 10 and the air flow meter AFM. The reforming air supply pipe L2has an air pump 11 and an on-off valve or a shut off valve 12 in thisorder from the branching point BP. A front end (an end opposite to thebranching point BP) of the reforming air supply pipe L2 is connected toa fuel reforming apparatus (fuel reformer) 20. In addition, as theon-off valve 12, a electromagnetic valve or a motorized valve may beadopted.

As shown in FIG. 2, the fuel reforming apparatus 20 has a tubular body21 closed at opposite ends thereof. An fuel injection valve 15 isconnected to one end of the body 21 (a right end in FIG. 2). The fuelinjection valve 15 is connected to a fuel tank via a fuel pump (notshown respectively) and is capable of injecting a hydrocarbon fuel suchas gasoline into the interior of the body 21.

As shown in FIG. 3, the fuel injection valve 15 is disposed within avalve accommodating section 22 connected to the body 21 of the fuelreforming apparatus 20. A front end of the reforming air supply pipe L2including the air pump 11 and the on-off valve 12 is connected to thevalve accommodating section 22, so that air is blown in the vicinity ofa fuel injection outlet 15 a of the fuel injection valve 15 in the valveaccommodating section 22. That is, the reforming air supply pipe L2 isconnected to the valve accommodating section 22 so that air is blown tothe fuel injection valve 15 (the fuel injection outlet 15 a) in thelateral direction.

Also, a nozzle member 16 is connected to a tip of the fuel injectionvalve 15. The nozzle member 16 has a plurality of air ejection outlets16 a extending radially, and an air-fuel mixing chamber 16 b extendingaxially and communicating with the respective air ejection outlets 16 a.The air-fuel mixing chamber 16 b of the nozzle member 16 is communicatedwith the interior of the body 21 of the fuel reforming apparatus 20 asshown in FIG. 3. O-rings 17 a, 17 b are interposed between the valveaccommodating section 22 and the fuel injection valve 15 as well as thenozzle member 16 for preventing the fuel or air from leaking outside.

On the other hand, a reforming reaction section 23 is defined in theinterior of the body 21 of the fuel reforming apparatus 20. A reformingcatalyst, for example, carrying rhodium on zirconium oxide is disposedin the reforming reaction section 23. As shown in FIG. 2, a cooler CLincluding a heat transfer tube wound around the body 21 is disposeddownstream of the reforming reaction section 23. In addition, the coolerCL may be omitted. Further, an adsorbent member (capturing means) 24 isdisposed downstream of the cooler CL in the interior of the body 21 ofthe fuel reforming apparatus 20. The adsorbent member 24 is obtained bycoating adsorbent material (such as zeolite) for adsorbing thehydrocarbon component (non-reformed HC) on a honeycomb member. Areformed fuel distribution chamber (a reformed fuel supply section) 25is defined downstream of the adsorbent member 24 in the interior of thebody 21 of the fuel reforming apparatus 20. That is, in the fuelreforming apparatus 20, the adsorbent member 24 is disposed between thereforming reaction section (reforming catalyst) 23 and the reformed fueldistribution chamber 25.

As shown in FIGS. 1 and 2, conduits 26 corresponding to the number ofthe combustion chambers 3 in the engine 1 (four in this embodiment) areconnected to the reformed fuel distributing chamber 25 in the body 21 ofthe fuel reforming apparatus 20. An end of the respective conduits 26 isconnected to the corresponding one intake pipe 5 a as shown in FIGS. 1and 2. Thus, the intake port of the respective combustion chambers 3 ofthe engine 1 is communicated with the interior of the reformed fueldistribution chamber 25 via the intake pipe 5 a and the pipe 26.

As shown in FIG. 1, the engine 1 of the vehicle 100 is provided with aelectronic control unit (hereinafter referred to as “ECU”) 30 serving ascontrol means. The ECU 30 includes CPU, ROM, RAM, input/outputinterfaces, memories (storage devices) and the like (not shown). Theabove-mentioned ignition plugs (igniter) 7, the valve operatingmechanism, the throttle valve 10, the air pump 11, the on-off valve 12,the fuel injection valve 15, the air flow meter AFM and the like areconnected to the ECU 30 (input/output interfaces). The ECU 30 controlsthese instruments based on signals from various sensors for detecting anoperational condition of the engine 1 and/or in accordance with variouscontrol programs or maps.

When the above described vehicle 100 is made to operate, the ECU 30makes the fuel injection valve 15 operate to start a fuel injection tothe fuel reforming apparatus 20. Almost simultaneously therewith, theECU 30 makes the on-off valve 12 open and makes the air pump 11 operate,so that air is supplied from the reforming air supply pipe L2 to thefuel reforming apparatus 20. The air pump 11 sucks air from the airsupply pipe L1 and discharges the air. Air discharged from the air pump11 is sent in the vicinity of the fuel injection outlet 15 a of the fuelinjection valve 15 in the valve accommodating section 22 through thereforming air supply pipe L2, and reaches the air-fuel mixing chamber 16b via the respective air ejection outlets 16 a. Air from the reformingair supply pipe L2 is mixed with the fuel injected from the fuelinjection outlets 15 a in the air-fuel mixing chamber 16 b of the nozzlemember 16, so that the a air mixture flows into the body 21 of the fuelreforming apparatus 20.

The fuel air mixture introduced into the interior of the body 21 flowsinto the reforming reaction section 23. In the reforming reactionsection 23, the hydrocarbon fuel and air are reacted each other by thereforming catalyst, so that the partially oxidation reaction representedby the following equation (1) is proceeded.

$\begin{matrix}{{{C_{m}H_{n}} + {\frac{m}{2} \cdot O_{2}}}->{{m \cdot {CO}} + {\frac{n}{2} \cdot H_{2}}}} & (1)\end{matrix}$

As the reaction of the above equation proceeds, the reformed fuel(reformed gas) containing fuel components of CO and H₂ is produced.

Now, it is not easy to uniformly mix the hydrocarbon fuel with air inthe air-fuel mixing chamber 16 b of the nozzle member 16 even in thefuel reforming apparatus 20. Particularly, immediately after a start-upof the fuel reforming apparatus 20, the supply of air to the air-fuelmixing chamber 16 b becomes unstable, and nonuniform fuel air mixturemay be supplied from the air-fuel mixing chamber 16 b of the nozzlemember 16 into the reforming reaction section 23. Therefore, an amountof non-reformed fuel (non-reformed HC) flowing out from the reformingreaction section 23 is liable to increase immediately after the start ofthe fuel reforming operation. In this embodiment, such a non-reformedfuel (non-reformed HC) contained in the reformed fuel is captured(adsorbed) between the reforming reaction section (reforming catalyst)23 and the reformed fuel distribution chamber 25 by the adsorbent member24 serving as capturing means. Particularly, since a temperature of theadsorbent member 24 is lowered approximately to an outer air temperatureimmediately after the start of the fuel reforming operation, thenon-reformed fuel is surely captured (adsorbed) by the adsorbent member24.

On the contrary, the reformed fuel (CO and H₂) obtained in the reformingreaction section 23 passes through the adsorbent member 24 without beingadsorbed thereby, and is supplied from the reformed fuel distributionchamber 25 to the interior of each intake pipe 5 a via the conduit 26.Moreover, air is introduced into the surge tank 8 via the throttle valve10 in the air supply pipe L1 which opening degree is controlled by theECU 30, and the air in the surge tank 8 is distributed to the respectiveintake pipes 5 a. Accordingly, the reformed fuel introduced from thereformed fuel distribution chamber 25 into each intake pipe 5 a is mixedwith air in the intake pipe 5 a and then sucked into the respectivecombustion chambers 3. In this embodiment, since air to be supplied tothe fuel reforming apparatus 20 is taken from the air supply pipe L1 ata point downstream of the air flow meter AFM, a measurement value of theair flow meter AFM indicates a total amount of air sucked into theengine 1, so that the air-fuel ratio in the respective combustionchambers 3 can be favorably controlled.

When the fuel air mixture of the reformed fuel and air is supplied tothe respective combustion chambers 3 and the ignition plugs 7 aredischarged at a predetermined timing, the fuel component CO and H₂ burnsto reciprocate the piston 4. Thus, the engine 1 operates to rotatewheels W via a trans-axle T including a torque converter, a transmissiongear box, a differential mechanism and the like. At this time, accordingto the fuel reforming apparatus 20, since the supply of the non-reformedfuel to the respective combustion chambers 3 of the engine 1 is surelyprevented, it is possible to reduce an exhaust emission and to enlarge alean combustion range so as to prevent NOx from increasing and a fuelconsumption rate from deteriorating.

The non-reformed fuel (non-reformed HC) adsorbed in the adsorbent member24 as described above is released from the adsorbent member 24 as thetemperature of the adsorbent member 24 rises, and introduced into therespective combustion chambers 3 via the reformed fuel distributionchamber 25, the conduit 26, the intake pipe 5 a and the like. In thisembodiment, the cooler CL is disposed between the reforming reactionsection 23 and the adsorbent member 24 to cool the reformed fuel flowingfrom the reforming reaction section 23 to the adsorbent member 24. Thatis, the reformed fuel of which temperature rises due to the reformingreaction in the reforming reaction section 23 is cooled by the coolerCL, and then, made to pass through the adsorbent member 24, so that atemperature rise of the adsorbent member 24 due to heat of the reformedfuel from the reforming reaction section 23 is eased (controlled). As aresult, since the non-reformed fuel is released from adsorbent member 24little by little as the time lapses, HC or others can be prevented frombeing discharged from the engine 1.

In addition, a coolant flowing through a heating tube of the cooler CLis preferably an engine coolant. If the engine coolant is used as thecoolant for the cooler CL, it is possible to sufficiently cool thereformed fuel from the reforming reaction section 23 since thetemperature of the engine coolant is enough low to favorably maintain acapacity of the adsorbent member 24 for adsorbing the non-reformed fuelwhen the fuel reforming apparatus 20 (the engine 1) is made to start.Further, if the engine coolant is used as the coolant for the cooler CL,since the temperature of the engine coolant rises as the engine 1becomes warmer, the reformed fuel from the reforming reaction section 23is not continuously excessively cooled. Thus, it is possible to releasethe non-reformed fuel from the adsorbent member 24 when the operation ofthe fuel reforming apparatus 20 and the combustion in the respectivecombustion chambers 3 are stable.

FIG. 4 is a partially sectional view illustrating an alteration of thefirst embodiment of the present invention. In a fuel reforming apparatus20A of FIG. 4, an adsorbent member 24A serving as capturing means is agenerally tubular honeycomb member which is coated with an adsorbentmaterial (such as zeolite) for adsorbing the hydrocarbon component(non-reformed HC). The adsorbent member 24A is generally tubular and anouter circumference of the adsorbent member 24A is fixed to an innercircumference of the body 21.

Generally, a mixing degree of the hydrocarbon fuel and air in a fuel airmixture flowing into the reforming reaction section (reforming catalyst)23 becomes better as being closer to a center (in the vicinity of anaxial center of the body 21), while it becomes richer in fuel as beingcloser to the outer circumference. Also, since a temperature of the body21 of the fuel reforming apparatus 20A is low upon the start of the fuelreforming operation, the non-reformed hydrocarbon fuel may be liquidizedif the fuel air mixture is in contact with the inner circumference ofthe body 21.

In view of the foregoing, since there is more non-reformed fuel as beingcloser to the outer circumference of the body 21, it is possible tosufficiently capture the non-reformed fuel by using the tubularadsorbent member 24A as in the fuel reforming apparatus 20A. Thus, it ispossible to reduce an amount of honeycomb member and adsorbent materialsuch as zeolite constituting the adsorbent member 24A, so that a weightand a production cost of the fuel reforming apparatus 20A can bereduced.

(Second Embodiment)

A second embodiment of the present invention will be described belowwith reference to FIGS. 5 to 8. The same elements as those describedwith reference to the first embodiment are referred to same referencenumerals and same description will be omitted.

A fuel reforming apparatus 20B according to the second embodiment of thepresent invention shown in FIG. 5 includes an on-off valve or a shut offvalve 27 disposed between the reforming reaction section 23 and thereformed fuel distribution chamber 25 in the interior of the body 21.The on-off valve 27 may be a motorized valve or the like of whichopening degree is controllable. An actuator (not shown) of the on-offvalve 27 is electrically connected to the ECU 30. A bypass pipe (asecond passage) 28 is connected to the body 21 which define a firstpassage connecting the reforming reaction section 23 and the reformedfuel distribution chamber 25, so that the bypass pipe 28 bypasses partthe body 21. That is, the bypass pipe 28 bypasses the on-off valve 27and directly connects the reforming reaction section 23 and the reformedfuel distribution chamber 25. An adsorbent member 24B is disposed in theinterior of the bypass pipe 28. The adsorbent member 24B is a honeycombmember which is coated with an adsorbent material (such as zeolite) foradsorbing the hydrocarbon component (non-reformed HC). Further, thebypass pipe 28 is provided with a temperature sensor 29 at a positiondirectly downstream of the adsorbent member 24B. The temperature sensor29 is electrically connected to the ECU 30. The temperature sensor 29detects a temperature of the reformed fuel flowing out from theadsorbent member 24B and provides the ECU 30 with a signal indicatingthe detected value.

The fuel reforming apparatus 20B is controlled by the ECU 30 inaccordance with a procedure shown in FIG. 6. In this case, the ECU 30makes the on-off valve 27 in the body 21 completely close prior to astart-up of the fuel reforming apparatus 20B (S10). After completelyclosing the on-off valve 27, the ECU 30 controls the fuel injectionvalve 15 to start a fuel injection into the fuel reforming apparatus20B. Almost simultaneously therewith, the ECU 30 makes the on-off valve12 open and makes the air pump 11 operate, so that air is supplied fromthe reforming air supply pipe L2 to the fuel reforming apparatus 20B(S12).

In such a manner, upon the start-up of the fuel reforming apparatus 20B,the on-off valve 27 is made to close and the reformed fuel and the likeare introduced from the reforming reaction section (reforming catalyst)23 only to the bypass pipe 28. Thus, a large amount of non-reformed fuelgenerally generated immediately after the start-up of the fuel reformingapparatus is captured by the adsorbent member 24B disposed in the bypasspipe 28, so that it is possible to prevent the non-reformed fuel frombeing supplied to the respective combustion chambers 3.

When the fuel reforming apparatus 20B is made to start at S12, the ECU30 obtains (estimates) a temperature T1 of the adsorbent member 24Bbased on the signal from the temperature sensor 29 (S14). Further, theECU 30 determines whether or not the temperature T1 of the adsorbentmember 24B obtained at S14 exceeds a predetermined threshold value Tr(S16). The threshold value Tr used at S16 is lower than a temperature atwhich an adsorbent ability of the adsorbent member 24B is lost, so thatit is possible to avoid the non-reformed fuel from not being adsorbed inthe adsorbent member 24B.

If it is determined at S16 that the temperature T1 of the adsorbentmember 24B exceeds the predetermined threshold value Tr, the ECU 30makes the on-off valve 27 open in accordance with a predeterminedcondition of the opening degree of the valve 27 (S18). That is, if thetemperature T1 of the adsorbent member 24B exceeds the predeterminedthreshold value Tr to stabilize an operational condition of the fuelreforming apparatus 20B, an amount of the non-reformed fuel decreasesand the non-reformed fuel adsorbed in the adsorbent member 24B isreleased from the adsorbent member 24B as the temperature of theadsorbent member 24B rises. Accordingly, when the operation of the fuelreforming apparatus 20B is stabilized in such a manner, the on-off valve27 is gradually made to open so that a flow rate of the reformed fuelflowing through the bypass pipe 28 reduces. Thus, it is possible tocontrol a temperature rise of the adsorbent member 24B due to heat ofthe high temperature reformed fuel and to release the non-reformed fuelfrom the adsorbent member 24B little by little as the time lapses. As aresult, according to the fuel reforming apparatus 20B, the discharge ofHC or others from the engine 1 is suppressed.

When the on-off valve 27 is made to open at S18, the ECU 30 terminatesthe procedure of FIG. 6 (a start-up operation of the fuel reformingapparatus 20B), and starts a control of the fuel reforming apparatus 20Bin a steady state. In addition, the description has been made in theabove described fuel reforming apparatus 20B that the on-off valve 27 ismade to open or close based on the temperature of the adsorbent member24B. However, the present invention should not be limited to this. Thatis, as described later, the on-off valve 27 may be controlled based onthe lapse of time from the start of the reforming reaction in thereforming reaction section 23. In such a case, the temperature sensor 29may be omitted from the bypass pipe 28. Also, at S18 of FIG. 6, theon-off valve 27 may be gradually made to open instead of beinginstantaneously (at once) made to open.

FIG. 7 is a partially sectional view illustrating an alteration of thefuel reforming apparatus according to the second embodiment of thepresent invention. In a fuel reforming apparatus 20C shown in FIG. 7,the body 21 is radially enlarged between the reforming reaction section23 and the reformed fuel distribution chamber 25 to form a largerdiametrical section 21a in which the on-off valve 27 is disposed. Theon-off valve 27 may be a motorized valve or the like of which openingdegree is controllable. An actuator (not shown) of the on-off valve 27is electrically connected to the ECU 30.

In the interior of the body 21, a short tubular member 31 is disposed tosurround the on-off valve 27. A total length of the tubular member 31 isshorter than that of the larger diametrical section 21 a of the body 21.An outer diameter (a cross-sectional area) of the tubular member 31 issubstantially equal to an outer diameter (a cross-sectional area) of thebody 21 (other than the larger diametrical section 21 a) and smallerthan an inner diameter of the larger diametrical section 21 a. Thetubular member 31 is fixed to the body 21 via a tubular adsorbent member24C which is positioned at a lengthwise center of the larger diametricalsection 21 a. The adsorbent member 24C is a honeycomb member coated withadsorbent material (for example, zeolite) for adsorbing hydrocarboncomponent (non-reformed HC). As shown in FIG. 7, the adsorbent member24C is fixed to the body 21 while being offset to the reformed fueldistribution chamber 25.

In the fuel reforming apparatus 20C, the interior of the tubular member31 defines a first passage connecting the reforming reaction section 23and the reformed fuel distribution chamber 25. Further, the tubularmember 31, i.e., the first passage is opened and closed by the on-offvalve 27. Also, a bypass passage (a second passage) 28C bypassing partof the first passage (the on-off valve 27) is defined between the outercircumference of the tubular member 31 and the inner circumference ofthe body 21, and the adsorbent member 24C is disposed in the bypasspassage 28. Further, a timer not shown is electrically connected to theECU 30 of the engine with the fuel reforming apparatus 20C.

The above described fuel reforming apparatus 20C is controlled by theECU 30 in accordance with a procedure shown in FIG. 8. In this case, theECU 30 makes the on-off valve 27 in the body 21 completely close priorto a start-up of the fuel reforming apparatus 20C (S20). Aftercompletely closing the on-off valve 27, the ECU 30 resets theabove-mentioned timer (S22). Further, the ECU 30 controls the fuelinjection valve 15 to start a fuel injection into the fuel reformingapparatus 20C. Almost simultaneously therewith, the ECU 30 makes theon-off valve 12 open and makes the air pump 11 operate, so that air issupplied from the reforming air supply pipe L2 to the fuel reformingapparatus 20C (S24).

As described above, in the fuel reforming apparatus 20C, the on-offvalve 27 is made to close upon the start-up thereof, and the reformedfuel is introduced only into the bypass passage 28C from the reformingreaction section 23 (the reforming catalyst). Thus, a large amount ofthe non-reformed fuel generally generated immediately after the start-upof the fuel reforming apparatus is captured by the adsorbent member 24Cdisposed in the bypass passage 28C, so that it is possible to preventthe non-reformed fuel from being supplied to the respective chambers 3.

When the fuel reforming apparatus 20C is made to start at S24, the ECU30 starts the timer substantially simultaneously therewith (S26). Then,the ECU 30 obtains a measurement time (lapse time) “t” of the timer(S28), and determines whether or not the obtained time “t” exceeds apredetermined threshold value “tr”, i.e., whether or not a predeterminedperiod has lapsed after the start-up of the fuel reforming apparatus 20C(S30). If it is determined at S30 that the measurement time “t” exceedsthe threshold value “tr”, the ECU 30 makes the on-off valve 27 open inaccordance with a predetermined condition of the opening degree (S32).

That is, since an operation of the fuel reforming apparatus 20C isstabilized when the predetermined time has lapsed after the start-up ofthe fuel reforming apparatus 20C, an amount of the non-reformed fuelfrom the reforming reaction section 23 reduces. Further, when thepredetermined time has lapsed after the start-up of the fuel reformingapparatus 20C, the temperature of the adsorbent member 24C becomes high,so that the non-reformed fuel adsorbed in the adsorbent member 24C isreleased from the adsorbent member 24C as the temperature of theadsorbent member 24C rises. Accordingly, by making the on-off valve 27open when the operation of the fuel reforming apparatus 20C is stable sothat a flow rate of the reformed fuel flowing through the bypass passage28C reduces, it is possible to control a temperature rise of theadsorbent member 24C due to heat from the hot reformed fuel, and thus torelease the non-reformed fuel little by little from the adsorbent member24C as the time lapses. As a result, it is possible to prevent HC orothers from discharging from the engine by the fuel reforming apparatus20C.

When the on-off valve 27 is made to open at S32, the ECU 30 terminatesthe procedure of FIG. 8 (a start-up operation of the fuel reformingapparatus 20C), and starts a control of the fuel reforming apparatus 20Cin a steady state. In addition, the description has been made in theabove described fuel reforming apparatus 20C that the on-off valve 27 ismade to open or close based on the lapse of time from the start of thereforming reaction in the reforming reaction section 23. However, thepresent invention should not be limited to this. That is, the timer maybe omitted and the bypass passage 28C may be provided with a temperaturesensor. In such a case, the on-off valve 27 may be controlled based onthe temperature of the adsorbent member 24C detected by the temperaturesensor. Also, at S32 of FIG. 8, the on-off valve 27 may be graduallymade to open instead of being instantaneously (at once) made to open.

(Third Embodiment)

A third embodiment of the present invention will be described below withreference to FIGS. 9 to 14. The same elements as those described withreference to the first embodiment are referred to same referencenumerals and same description will be omitted.

In comparison with the fuel reforming apparatus 20B of FIG. 5, a fuelreforming apparatus 20D shown in FIG. 9 further includes non-reformedfuel recovering means for recovering the non-reformed fuel captured bythe adsorbent member (capturing means) 24B and supplying thenon-reformed fuel again to the reforming reaction section (reformingcatalyst) 23. According to the fuel reforming apparatus 20D, thenon-reformed fuel is surely prevented from being supplied to therespective combustion chambers 3 and the non-reformed fuel captured bythe adsorbent member 24B is recovered and effectively used again.

The detailed description of the fuel reforming apparatus 20D of FIG. 9will be described in more detail below. The fuel reforming apparatus 20Dincludes a first on-off valve (shut off valve) 27 a for opening andclosing the body 21 which defines a first passage connecting thereforming reaction section 23 and the reformed fuel distribution chamber25. Further, fuel reforming apparatus 20D includes a second on-off valve27 b for opening and closing an inlet of the bypass pipe 28 (a meetingpoint between the bypass pipe 28 and the body 21 on a side of thereforming reaction section 23). The first on-off valve 27 a and thesecond on-off valve 27 b may be a motorized valve and the like.Actuators (not shown) of the on-off valves 27 a and 27 b areelectrically connected to the ECU 30.

One end of a purge pipe L4 is connected to the bypass pipe 28. In thisembodiment, the purge pipe L4 is connected to the bypass pipe 28 betweenthe second on-off valve 27 b and the adsorbent member 24B. However, thepurge pipe L4 may be connected to the bypass pipe 28 downstream of theadsorbent member 24B. On the other hand, a Venturi tube (negativepressure generating means) 32 is disposed in the interior of thereforming air supply pipe L2 for supplying air to the fuel reformingapparatus 20D between the on-off valve 12 and the valve accommodatingsection 22.

The Venturi tube 32 is formed as a tubular member having a narrowestportion (a throat) of the minimum inner diameter at a lengthwise centerthereof. The other end of the above-mentioned purge pipe L4 penetratesthe reforming air supplying pipe L2, and penetrates a lengthwise centerof the Venturi tube 32 to confront the narrowest portion in the Venturitube 32.

In this case, air delivered by the air pump 11 flows the interior of theVenturi tube 32 in the reforming air supply pipe L2, and a velocity ofthe air is highest in the vicinity of the narrowest portion of theVenturi tube 32 having the minimum inner diameter, i.e., in the vicinityof the connecting point (meeting point) with the purge pipe L4.Accordingly, the Venturi tube 32 serves as means for generating anegative pressure in the interior of the reforming air supply pipe L2between the on-off valve 12 and the valve accommodating section 22.

The fuel reforming apparatus 20D is controlled by the ECU 30 inaccordance with a procedure shown in FIG. 10. In this case, the ECU 30makes the first on-off valve 27 a disposed in the body 21 completelyclose, and makes the second on-off valve 27 b disposed at the inlet ofthe bypass pipe 28 completely open (S40). Then, the ECU 30 controls thefuel injection valve 15 to start a fuel injection into the fuelreforming apparatus 20D. Almost simultaneously therewith, the ECU 30makes the on-off valve 12 open and makes the air pump 11 operate, sothat air is supplied from the reforming air supply pipe L2 to the fuelreforming apparatus 20D (S42).

In the fuel reforming apparatus 20D, upon the start-up thereof, thefirst on-off valve 27 a is made to close and the second on-off valve 27b is made to open, so that the reformed fuel from the reforming reactionsection (reforming catalyst) 23 is introduced only into the bypass pipe28. Thus, a large amount of non-reformed fuel generally generatedimmediately after the start-up of the fuel reforming apparatus iscaptured by the adsorbent member 24B disposed in the bypass pipe 28, sothat the non-reformed fuel is prevented from being supplied to therespective combustion chambers 3.

When the fuel reforming apparatus 20D is made to start at S42, the ECU30 obtains (estimates) a temperature T1 of the adsorbent member 24Bbased on the signal from the temperature sensor 29 (S44). Further, theECU 30 determines whether or not the temperature T1 of the adsorbentmember 24B obtained at S44 exceeds a predetermined threshold value Tr(S46). The threshold value Tr is set at a value lower than a temperatureat which an adsorbent ability of the adsorbent member 24B is lost, sothat it is possible to avoid a situation in which the non-reformed fuelis not adsorbed in the adsorbent member 24B.

If it is determined at S46 that the temperature T1 exceeds the thresholdvalue Tr, the ECU 30 makes the first on-off valve 27 a open and makesthe second on-off valve 27 b close (S48). That is, if the temperature T1of the adsorbent member 24B exceeds the threshold value Tr to stabilizethe operation of the fuel reforming apparatus 20D, an amount of thenon-reformed fuel decreases. Therefore, it is possible to prevent HC orothers from being discharged from the engine 1 even if the adsorbent ofthe non-reformed fuel in the adsorbent member 24B is stopped. Also,since the negative pressure is generated in the vicinity of the inlet ofthe bypass pipe 28 by an operation of the Venturi tube 32 in the fuelreforming apparatus 20D as described above, the non-reformed fuelcaptured by the adsorbent member 24B is sucked into the reforming airsupply pipe L2 when the second on-off valve 27 b is closed to interruptthe reformed fuel to flow into the bypass pipe 28. The non-reformed fuelsucked into the reforming air supply pipe L2 is supplied again to thereforming reaction section 23 after being mixed with air. In such amanner, according to the fuel reforming apparatus 20D, it is possible torecover the non-reformed fuel captured by the adsorbent member 24B andeffectively use the non-reformed fuel again.

When the process at S48 has completed, the ECU 30 terminates theprocedure of FIG. 10 (a start-up operation of the fuel reformingapparatus 20D) and starts a control of the fuel reforming apparatus 20Din a steady state. In addition, the description has been made in theabove described fuel reforming apparatus 20D that the on-off valves 27 aand 27 b are made to open or close based on the temperature of theadsorbent member 24B. However, the present invention should not belimited to this. That is, the on-off valves 27 a and 27 b may becontrolled based on the lapse of time from the start of the reformingreaction in the reforming reaction section 23. In such a case, thetemperature sensor 29 may be omitted from the bypass pipe 28.

FIG. 11 is a partially sectional view of an alteration of the thirdembodiment according to the present invention. A fuel reformingapparatus 20E shown in FIG. 11 corresponds to the fuel reformingapparatus 20C of FIG. 7 further including means for recovering thenon-reformed fuel captured by the adsorbent member (capturing means) 24Cand supplying the non-reformed fuel again to the reforming reactionsection (reforming catalyst) 23. By the fuel reforming apparatus 20E, itis possible to surely prevent the non-reformed fuel from being suppliedto the respective combustion chambers 3, and to recover the non-reformedfuel captured by the adsorbent member 24C to effectively use thenon-reformed fuel again.

The fuel reforming apparatus 20E of FIG. 11 will be described in moredetail below. In the fuel reforming apparatus 20E, a tubular member 31Eextends toward the reformed fuel distribution chamber 25 to close thedownstream side end of the bypass passage 28C. One end of a connectingpipe L5 is connected to a closed space defined by the larger diametricalsection 21 a of the body 21, the tubular member 31E and the adsorbentmember 24C. The other end of the connecting pipe L5 is connected to afirst port of a three-way valve 33. Also, one end of a connecting pipeL6 is connected to a second port of the three-way valve 33. The otherend of the connecting pipe L6 is connected to the body 21 at a positioncloser to the reformed fuel distribution chamber 25 rather than to thelarger diametrical section 21 a. Further, one end of the purge pipe L4is connected to a third port of the three-way valve 33. The other end ofthe purge pipe L4 penetrates the reforming air supply pipe L2 and thelengthwise center of the Venturi tube 32 to confront the narrowestportion in the Venturi tube 32.

The three-way valve 33 is capable of switching passages between a bypassside and a purge side. If the three-way valve 33 is switched to thebypass side, the bypass passage 28 c is connected to the interior of thebody 21 (first passage) downstream of the larger diametrical section 21a via the connecting pipes L5 and L6. On the other hand, if thethree-way valve 33 is switched to the purge side, the bypass passage 28Cis connected to the reforming sir supply pipe L2 via the connecting pipeL5 and the purge pipe L4. The three-way valve 33 is electricallyconnected to the ECU 30 and controlled by the ECU 30. Also, a timer notshown is electrically connected to the ECU 30 for the engine with thefuel reforming apparatus 20E.

The fuel reforming apparatus 20E is controlled by the ECU 30 inaccordance with a procedure shown in FIG. 12. In this case, the ECU 30makes the on-off valve 27 provided in the body 21 completely close priorto a start-up of the fuel reforming apparatus 20E (S50). After theon-off valve 27 has completely been closed, the ECU 30 switches thethree-way valve 33 to the bypass side (S52). Thus, the bypass passage28C is connected to the interior of the body 21 (the first passage)downstream of the larger diametrical section 21 a via the connectingpipes L5 and L6. Then, the ECU 30 resets the above-mentioned timer(S54), and controls the fuel injection valve 15 to start a fuelinjection into the fuel reforming apparatus 20E. Almost simultaneouslytherewith, the ECU 30 makes the on-off valve 12 open and makes the airpump 11 operate, so that air is supplied from the reforming air supplypipe L2 to the fuel reforming apparatus 20E (S56).

In the fuel reforming apparatus 20E, the on-off valve 27 is made toclose upon the start-up thereof so as to allow the reformed fuel to beintroduced from the reforming reaction section (reforming catalyst) 23only to the bypass passage 28C. Thus, a large amount of non-reformedfuel generally generated immediately after the start-up of the fuelreforming apparatus is captured by the adsorbent member 24C disposed inthe bypass passage 28C, so that it is possible to prevent thenon-reformed fuel from being supplied to the respective combustionchambers 3. The reformed fuel passing through the adsorbent member 24Cin the bypass passage 28C is returned into the interior of the body 21via the connecting pipes L5, L6 and supplied to the reformed fueldistribution chamber 25.

When making the fuel reforming apparatus 20E start at S56, the ECU 30starts the timer substantially simultaneously therewith (S58). The ECU30 obtains a measurement time (lapse time) “t” of the timer (S60), anddetermines whether or not the time “t” thus obtained exceeds apredetermined threshold value “tr”, that is, whether or not apredetermined period has lapsed after the start-up of the fuel reformingapparatus 20C (S62). If it is determined at S62 that the measurementtime “t” exceeds the predetermined threshold value “tr”, the ECU 30makes the on-off valve 27 open (S64), and then, switches the three-wayvalve 33 to the purge side (S66).

That is, since the operation of the fuel reforming apparatus 20E isstabilized when the predetermined time has lapsed after the start-up ofthe fuel reforming apparatus 20E, an amount of non-reformed fuelreduces. Thus, it is possible to suppress the discharge of HC or othersfrom the engine 1 even if the non-reformed fuel is not captured by theadsorbent member 24C. Further, in the fuel reforming apparatus 20E, anegative pressure is generated in the interior of a closed space definedby the larger diametrical section 21a, the tubular member 31E and theadsorbent member 24C via the purge pipe L4 and the connecting pipe L5due to an operation of the Venturi tube 32, when the three-way valve 33is switched to the purge side. Accordingly, the non-reformed fuelcaptured by the adsorbent member 24C is sucked into the reforming airsupply pipe L2 via the connecting pipe L5 and the purge pipe L4. Thenon-reformed fuel sucked into the reforming air supply pipe L2 issupplied again to the reforming reaction section 23 after being mixedwith air. As described above, in the fuel reforming apparatus 20E, it ispossible to recover the non-reformed fuel captured by the adsorbentmember 24C and effectively use the non-reformed fuel again.

After switching the three-way valve 33 to the purge side as S66, the ECU30 terminates the procedure of FIG. 12 (a start-up operation of the fuelreforming apparatus 20E), and starts a control of the fuel reformingapparatus 20E in a steady state. In addition, the description has beenmade in the above described fuel reforming apparatus 20E that the on-offvalve 27 and/or the three-way valve 33 are controlled based on the lapseof time from the start of the reforming reaction in the reformingreaction section 23. However, the present invention should not belimited to this. That is, the timer may be omitted and a temperaturesensor may be disposed in the bypass passage 28C so that the on-offvalve 27 and/or the three-way valve 33 may be controlled based on atemperature of the adsorbent member 24C detected by the temperaturesensor.

FIG. 13 is a partially sectional view of another alteration according tothe third embodiment of the present invention. A fuel reformingapparatus 20F shown in FIG. 13 corresponds to the fuel reformingapparatus 20A of FIG. 4 further including means for recovering thenon-reformed fuel captured by the capturing means and supplying thenon-reformed fuel again to the reforming reaction section (reformingcatalyst) 23. By the fuel reforming apparatus 20F, it is possible tosurely prevent the non-reformed fuel from being supplied to therespective combustion chambers 3, and to recover the non-reformed fuelcaptured by the adsorbent member to effectively use the non-reformedfuel again. Since this fuel reforming apparatus 20F is relatively simplein construction, it can be formed at a lower cost without increasing aweight thereof.

The fuel reforming apparatus 20F of FIG. 13 will be described in moredetail below. In this fuel reforming apparatus 20F, a tubular adsorbentmember 24F which is a honeycomb member coated with adsorbent material(such as zeolite) for adsorbing hydrocarbon component (non-reformed HC)is disposed in the interior of the body 21 between the reformingreaction section (reforming catalyst) 23 and the reformed fueldistribution chamber 25. A closed space 35 is defined in the vicinity ofa rear end of the adsorbent member 24F by the body 21, an annular member34 fixed to the inner circumference of the body 21 and the adsorbentmember 24F.

One end of the connecting pipe L5 is connected to the closed space 35.The other end of the connecting pipe L5 is connected to a first port ofthe three-way valve 33. One end of the connecting pipe L6 is connectedto a second port of the three-way valve 33. The other end of theconnecting pipe L6 is connected to the body 21 on a side closer to thereformed fuel distribution chamber 25 rather than to the closed space35. Further, one end of the purge pipe L4 is connected to a third portof the three-way valve 33. The other end of the purge pipe L4 penetratesthe reforming air supply pipe L2 and a lengthwise center of the Venturitube 32 to confront the narrowest portion in the Venturi tube 32. Aswell as the fuel reforming apparatus 20E of FIG. 11, the three-way valve33 is capable of switching passages between a bypass side and a purgeside. Also, a timer not shown is connected to the ECU 30 of the enginewith the fuel reforming apparatus 20F.

The fuel reforming apparatus 20F is controlled by the ECU 30 inaccordance with a procedure shown in FIG. 14. In this case, the ECU 30switches the three-way valve 33 to the bypass side prior to a start-upof the fuel reforming apparatus 20F (S70). Thus, the closed space 35 isconnected to the interior of the body 21 downstream thereof via theconnecting pipes L5 and L6. Then, the ECU 30 resets the above-mentionedtimer (S72), and controls the fuel injection valve 15 to start a fuelinjection into the fuel reforming apparatus 20F. Almost simultaneouslytherewith, the ECU 30 makes the on-off valve 12 open and makes the airpump 11 operate, so that air is supplied from the reforming air supplypipe L2 to the fuel reforming apparatus 20F (S74). A large amount ofnon-reformed fuel generated immediately after the start of the operationof the fuel reforming apparatus is captured by the tubular adsorbentmember 24F disposed in the interior of the body 21, so that it ispossible to prevent the non-reformed fuel from being supplied to therespective combustion chambers 3.

When the fuel reforming apparatus 20F is made to start at S74, the ECU30 starts the timer substantially simultaneously therewith (S76). TheECU 30 obtains a measurement time (lapse time) “t” of the timer (S78),and determines whether or not the obtained measurement time “t” exceedsa predetermined threshold value “tr1”, that is, whether or not apredetermined time has lapsed after has been made to start 20F (S80). Ifit is determined that the measurement time “t” exceeds the predeterminedthreshold value “tr1”, the ECU 30 switches the three-way valve 33 to thepurge side (S82).

When the three-way valve 33 is switched to the purge side in such amanner, a negative pressure is generated in the interior of the closedspace 35 via the purge pipe L4 and the connecting pipe L5 due to anoperation of the Venturi tube 32. Thus, the non-reformed fuel capturedby the adsorbent member 24F is sucked into the reforming air supply pipeL2 via the connecting pipe L5 and the purge pipe L4. The non-reformedfuel sucked into the reforming air supply pipe L2 is supplied again tothe reforming reaction section 23 after being mixed with air. As aresult, it is possible to recover the non-reformed fuel captured by theadsorbent member 24F and effectively use again in the fuel reformingapparatus 20F.

When switching the three-way valve 33 to the purge side at S82, the ECU30 obtains the measurement time (lapse time) “t” of the timer (S84), anddetermines whether or not the measurement time “t” thus obtained exceedsa predetermined threshold value “tr2” (S86). If it is determined at S86that the measurement time “t” exceeds the predetermined threshold value“tr2”, the ECU 30 switches the three-way valve 33 again to the bypassside (S88). Thus, the reformed fuel (CO and H₂) produced by thereforming catalyst is prevented from being introduced again into thereforming catalyst via the purge pipe L4 and the like, in which CO andH₂ changes to CO_(2 and H) ₂O respectively.

When switching the three-way valve 33 to the bypass side at S88, the ECU30 terminates the procedure of FIG. 14 (a start-up operation of the fuelreforming apparatus 20F) and starts a control of the fuel reformingapparatus 20F in a steady state. In addition, the description has beenmade in the above described fuel reforming apparatus 20F that thethree-way valve 33 is controlled based on the time lapse from the startof the reforming reaction in the reforming reaction section 23. However,the present invention should not be limited to this. That is, the timermay be omitted and a temperature may be disposed in the vicinity of theadsorbent member 24F. In such a case, the three-way valve 33 may becontrolled based on the temperature of the adsorbent member 24F detectedby the temperature sensor.

(Fourth Embodiment)

A fourth embodiment of the present invention will be described belowwith reference to FIGS. 15 to 18. The same elements as those describedwith reference to the first embodiment are referred to same referencenumerals and same description will be omitted.

A fuel reforming apparatus 20G shown in FIG. 15 has a heat exchanger 200between the reforming reaction section 23 and the reformed fueldistribution chamber 25. The heat exchanger 200 includes a plurality ofreformed fuel flowing pipes 201 made of a heat-conductive material suchas a metal and a pair of closure plates 202 as shown in FIGS. 15 and 16.The closure plates 202 respectively include the same number of holes asthat of the reformed fuel flowing pipes 201, and are disposed at apredetermined interval for partitioning between the reforming reactionsection 23 and the reformed fuel distribution chamber 25. Opposite endsthe respective reformed fuel flowing pipes 201 are inserted into theholes of the respective closure plates 202 and fixed thereto.

Thus, a reformed fuel passage 203 for leading the reformed fuel flowingout from the reforming reaction section 23 to the reformed fueldistribution chamber (the reformed fuel supplying section) 25 is definedby the reformed fuel flowing pipe 201. Also, a coolant passage 204 isdefined around the reformed fuel flowing pipes 201 by the body 21 andthe respective closure plates 202. On the inner surface of the each ofthe reformed fuel flowing pipes 201, a coating layer 240 of adsorbentmaterial (such as zeolite) for adsorbing hydrocarbon component(non-reformed HC) is applied.

Further, the body 21 is provided with a coolant inlet 205 and a coolantoutlet 206 respectively communicating with the coolant passage 204 ofthe body 21. As shown in FIG. 17, one end of an air feeding pipe L201 isconnected to the coolant inlet 205, and the other end of the air feedingpipe L201 is connected to the air supply pipe L1 upstream of thethrottle valve 10. The air feeding pipe L201 has a flow control valve207 of which opening degree is controlled by the ECU 30 in the midwaythereof.

One end of an air returning pipe L202 is connected to the coolant outlet206, and the other end of the air returning pipe L202 is connected tothe air supply pipe L1 between the throttle valve 10 and the surge tank8. Thus, if the flow control valve 207 is made to open, part (or all) ofair (sucked air) in the air supply pipe L1 is introduced into thecoolant passage 204 of the heat exchanger 200, and returned to the airsupply pipe L1 via the air returning pipe L202.

In the fuel reforming apparatus 20G, when the reformed fuel (reformedgas) containing fuel components CO and H₂ is produced in the reformingreaction section 23, the reformed fuel flows out from the reformingreaction section 23 to the respective reformed fuel flowing pipes 201(the reformed fuel passages 203) of the heat exchanger 200, and broughtinto contact with the coating layer 240 of the adsorbent materialapplied to the inner surface of the respective reformed fuel flowingpipes 201. Thus, the non-reformed fuel (non-reformed HC) contained inthe reformed fuel from the reforming reaction section 23 is surelycaptured (adsorbed) by the coating layer 240 of the adsorbent material.

During an operation of the fuel reforming apparatus 20G, the ECU 30makes the flow control valve 207 of the air feeding pipe L201 open andcontrols the opening degree of the flow control valve 207 in accordancewith a predetermined condition. Thus, part (or all) of the air takeninto the air supply pipe L1 flows into the air feeding pipe L201, and isintroduced into the coolant passage 204 of the hear exchanger 200 viathe air feeding pipe L201. Air or a coolant flowing into the coolantpassage 204 absorbs heat from the reformed fuel flowing through therespective reformed fuel flowing pipes 201 (the reformed fuel passage203) and a temperature thereof becomes high. Then, the air in thecoolant passage 204 is sucked into the interior of the air supply pipeL1 (the surge tank 8) via the air returning pipe L202.

In such a manner, the reformed fuel in each reformed fuel flowing pipe201 is cooled in the fuel reforming apparatus 20G due to the heatexchange between the reformed fuel and air as the coolant, so that thetemperature of the coating layer 240 in contact with the reformed fuelis surely prevented from excessively rising. Accordingly, it is possibleto surely capture (adsorb) the non-reformed fuel contained in thereformed fuel from the reforming reaction section 23 by the coatinglayer 240 of the adsorbent material. Also, it is possible to release thenon-reformed fuel thus captured from the coating layer 240 little bylittle as the time has lapsed.

As a result, according to the fuel reforming apparatus 20G, it ispossible to prevent the non-reformed fuel from being supplied to therespective combustion chambers of the engine and to surely burn thenon-reformed fuel in the respective combustion chamber. Thus, an exhaustemission reduces and the lean combustion range is enlarged to preventNOx from increasing as well as the fuel consumption from deteriorating.Also, according to the fuel reforming apparatus 20G, hot air heated bythe reformed fuel in the heat exchanger 200 is supplied to therespective combustion chambers. Thus, it is possible to accelerate thewarm-up of the engine.

Further, according to the fuel reforming apparatus 20G, the coatinglayer 240 of the adsorbent material is substantially cooled by air asthe coolant. Thus, it is possible to improve the durability of thecoating layer 240. Since air is introduced into the coolant passage 204of the heat exchanger 200 by using the negative pressure generated inthe respective combustion chambers (the surge tank 8) in the fuelreforming apparatus 20G, it is unnecessary to use a power source such asan exclusive pump or others for introducing the heat transfer medium(air) into the heat exchanger.

Now, while a boiling point (a releasing temperature from the coatinglayer 240) of hydrocarbon fuel such as gasoline is approximately 200°C., air supplied to the coolant passage 204 of the heat exchanger 200 inthe fuel reforming apparatus 20G is basically at an ordinarytemperature. Accordingly, if air is always supplied to the heatexchanger 200 of the fuel reforming apparatus 20G via the air feedingpipe L201, in a certain operational condition of the fuel reformingapparatus 20G (the engine provided therewith), there may be a case inwhich it is difficult to raise the temperature of the coating layer 240applied to the inner surface of the respective reformed fuel flowingpipes 201 to a value at which the non-reformed fuel is released from thecoating layer 240.

In view of such points, when it is necessary to release the non-reformedfuel from the coating layer 240 or when a predetermined condition isestablished, the ECU 30 in this embodiment makes the flow control valve207 in the air feeding pipe L201 close for a predetermined period. Thus,the heat exchange is not carried out between the reformed fuel and airin the heat exchanger 200 of the fuel reforming apparatus 20G. As aresult, it is possible to raise the temperature of the coating layer 240of the respective reformed fuel flowing pipes 201 by the heat of thereformed fuel from the reforming reaction section 23 so at to surelyrelease the non-reformed fuel from the coating layer 240. In this case,if a closed time of the flow control valve 207 is limited (i.e., if itis not unnecessarily prolonged), it is possible to surely prevent thetemperature of the coating layer 240 from excessively rising, thereby tofavorably maintain the durability of the coating layer 240.

FIG. 18 is a schematic illustration of an alteration of the fuelreforming apparatus according to the fourth embodiment of the presentinvention. While a fuel reforming apparatus 20H shown in FIG. 18 has asubstantially the same structure as the above described fuel reformingapparatus 20G, an engine coolant from an engine cooling system 300 issupplied as a coolant to the heat exchanger 200 of the fuel reformingapparatus 20H, instead of sucked air.

As shown in FIG. 18, the engine cooling system 300 for circulating theengine coolant to the cylinder block 2 and the like includes an enginecoolant pump 301, a thermostat 302 and a radiator 303. An engine coolantsupply pipe L301 is branched from the engine cooling system 300 on anoutlet side of the engine coolant pump 301. An end of the engine coolantsupply pipe L301 is connected to the coolant inlet 205 of the heatexchanger 200 in the fuel reforming apparatus 20H. Also, one end of anengine coolant returning pipe L302 is connected to the coolant outlet206 of the heat exchanger 200 in the fuel reforming apparatus 20H, andthe other end of the engine coolant returning pipe L302 is connected tothe engine cooling system 300 upstream of a inlet of the radiator 303.The engine coolant returning pipe L302 has a flow control valve 304controlled by the ECU 30 in the midway thereof.

The ECU 30 makes the flow control valve 304 of the engine coolantreturning pipe L302 open during an operation of the fuel reformingapparatus 20H of FIG. 18, and controls an opening degree of the flowcontrol valve 304 in accordance with a predetermined condition. Thus,part of the engine coolant discharged from the engine coolant pump 301flows into the engine coolant supply pipe L301 and is introduced intothe coolant passage 204 of the heat exchanger 200 in the fuel reformingapparatus 20H via the engine coolant supply pipe L301. The enginecoolant flowing into the coolant passage 204 is sent to the radiator 303via the engine coolant returning pipe L302 after absorbing heat from thereformed fuel flowing through the respective reformed fuel passages 203in the heat exchanger 200.

As described above, according to the fuel reforming apparatus 20H, thereformed fuel in the respective reformed fuel passages 203 is cooled bythe heat exchange between the reformed fuel and the engine coolant.Therefore, it is possible to surely prevent the temperature of thecoating layer in contact with the reformed fuel from excessively rising.Accordingly, it is possible to surely capture (adsorb) the non-reformedfuel contained in the reformed fuel from the reforming reaction section23, and to release the non-reformed fuel from the coating layer littleby little as the time has lapsed.

As a result, also in the fuel reforming apparatus 20H, the non-reformedfuel can be prevented from being supplied to the respective combustionchambers of the engine and combustion of the non-reformed fuel in therespective combustion chambers is assured. Thus, it is possible toreduce an exhaust emission and to enlarge a lean combustion range toprevent NOx from increasing as well as to avoid the deterioration offuel consumption.

According to the fuel reforming apparatus 20H, since the coating layerof the adsorbent material is substantially cooled by the engine coolantas described above, the durability of the coating layer is improved.Also, in the fuel reforming apparatus 20H, since the engine coolant isintroduced into the coolant passage 204 of the heat exchanger 200 byusing the engine coolant pump 301, it is unnecessary to use an exclusivepower source for introducing the heating medium into the heat exchanger.

Further, according to the fuel reforming apparatus 20H of FIG. 18, theflow control valve 304 in the engine coolant returning pipe L302 isclosed for the predetermined period if there is a requirement forreleasing the non-reformed fuel from the coating layer of the adsorbentmaterial, or if the predetermined condition is established. Thus, theheat exchanging is not carried out between the reformed fuel and theengine coolant in the heat exchanger 200 of the fuel reforming apparatus20H, so that it is possible to raise the temperature of the coatinglayer of the adsorbent material in the respective reformed fuel passages203 by heat of the reformed fuel from the reforming reaction section 23to surely release the non-reformed fuel from the coating layer. Also inthis case, by limiting a period for closing the flow control valve 304,it is possible to surely prevent the temperature of the coating layer ofthe adsorbent material from excessively rising and favorably maintainthe durability of the coating layer.

The present invention has been described in detail with respect topreferred embodiments, and it will now be apparent from the foregoing tothose skilled in the art that changes and modifications may be madewithout departing from the invention in its broader aspect, and it isthe intention, therefore, in the apparent claims to cover all suchchanges and modifications as fall within the true spirit of theinvention.

1. A fuel reforming apparatus for reforming a fuel air mixture of a fueland air, comprising: a reforming catalyst for reforming said fuel airmixture; a reformed fuel supply section for supplying a reformed fuelproduced by said reforming catalyst to a predetermined object; capturingmeans for capturing a non-reformed fuel, said capturing means beingdisposed between said reforming catalyst and said reformed fuel supplysection; and cooling means for cooling said reformed fuel between saidreforming catalyst and said capturing means, the cooling means being aheat exchanging means having a reformed fuel passage for leading saidreformed fuel from said reforming catalyst to said reformed fuel supplysection and a heating medium passage for circulating a heating medium toexchange heat between said heating medium and said reformed fuel flowingthrough said reformed fuel passage; and the capturing means being anadsorbent material for adsorbing said non-reformed fuel in said reformedfuel passage of said heat exchanging means.
 2. The fuel reformingapparatus of claim 1, wherein said capturing means is disposed in anouter region of a passage connecting said reforming catalyst and saidreformed fuel supply section.
 3. The fuel reforming apparatus of claim1, further comprising: a first passage connecting said reformingcatalyst and said reformed fuel supply section; a second passagebypassing part of said first passage and connecting said reformingcatalyst and said reformed fuel supply section; and opening/closingmeans for opening and closing said first passage, wherein said capturingmeans is disposed in said second passage and includes an adsorbentmaterial for adsorbing said non-reformed fuel.
 4. The fuel reformingapparatus of claim 3, wherein said second passage connecting a portionof said first passage upstream of said opening/closing means and aportion of said first passage downstream of said opening/closing means.5. The fuel reforming apparatus of claim 4, wherein said second passagesurrounds said first passage.
 6. The fuel reforming apparatus of claim3, wherein said opening/closing means is closed from a start of a fuelreforming operation in said reforming catalyst until a predeterminedperiod has lapsed, or until said adsorbent material has reached apredetermined temperature.
 7. The fuel reforming apparatus of claim 1,further comprising non-reformed fuel recovering means for recoveringsaid non-reformed fuel captured by said capturing means and supplyingsaid non-reformed fuel to said reforming catalyst again.
 8. The fuelreforming apparatus of claim 7, wherein said non-reformed fuelrecovering means comprises: negative pressure generating means forgenerating a negative pressure by using a flow of air supplied to saidreforming catalyst; and a passage connecting said negative pressuregenerating means and said capturing means.
 9. The fuel reformingapparatus of claim 1, wherein said predetermined object is a combustionchamber of an internal combustion engine, and wherein said heatingmedium is part of air supplied to said combustion chamber.
 10. A methodof reforming a fuel air mixture of a fuel and air with a reformingcatalyst, comprising: providing a reformed fuel through a reformed fuelpassage between the reforming catalyst and a reformed fuel supplysection, for supplying a reformed fuel produced by the reformingcatalyst to a predetermined object; capturing a non-reformed fuel withinsaid reformed fuel passage with an adsorbent material; and cooling saidreformed fuel by a heat exchanging means having said reformed fuelpassage and a heating medium passage for circulating a heating medium toexchange heat between said heating medium and said reformed fuel flowingthrough said reformed fuel passage.
 11. The method of claim 10, furthercomprising: cooling said reformed fuel between said reforming catalystand a capturing means.
 12. The method of claim 10, further comprising:recovering said non-reformed fuel captured by said adsorbent materialand supplying said non-reformed fuel to said reforming catalyst again.